As an example of headlight control for controlling a headlight of a host vehicle, there is light distribution control to detect a preceding vehicle or an oncoming vehicle and switch the headlight of the host vehicle from a high beam to a low beam, to prevent dazzling of a driver of the preceding vehicle or the oncoming vehicle due to the high beam of the headlight of the host vehicle in night travelling. In the light distribution control, a region of high brightness is searched for and extracted as a light spot to detect a taillight of the preceding vehicle or a headlight of the oncoming vehicle from an image imaged by a camera.
When an image is imaged by a shutter subjected to automatic exposure adjustment like a normal external recognition application, an exposure time may be too long, which may result in overexposure, or the exposure time may be too short, which may not extract the light spot accurately. Therefore, in the light distribution control, it is necessary to image an image with a constant exposure time.
However, when the image is imaged with the constant exposure time, exposure times suitable for a distant light source object and a proximal light source object are different from each other. For this reason, images with a plurality of different exposure times such as an image imaged with an exposure time for a distant light spot and an image imaged with an exposure time for a proximal light spot are required.
Because the brightness of the taillight of the preceding vehicle and the headlight of the oncoming vehicle to be extracted as light spots are also different from each other, exposure times suitable for the taillight and the headlight are different from each other. For this reason, images with different exposure times are required for detection of the taillight of the preceding vehicle and for detection of the headlight of the oncoming vehicle.